We will continue to study the origin, circulation, and fate of synaptic vesicles in neurons and in retinal photoreceptors, using combined electron microscopic and cytochemical techniques. We hope to obtain a clearer picture of the details of synaptic functioning and of the turnover of the membranes and other components involved in such functioning. One principal focus of our work will be evaluation of synaptic activities of the neurons and photoreceptors under varying physiological conditions. We also will investigate aspects of intraneuronal transport, especially participation of the agranular endoplasmic reticulum, and we will deal with features of intracellular digestion, in which lysosomes are central agents and retograde transport processes seem to be involved. In addition, we will continue to work on the distribution and other features of peroxisomes in nervous tissue.